1. Technical Field of the Invention
This invention relates generally to infrared (IR) communication systems and more particularly to programmable IR data processors in such IR communications systems.
2. Description of the Related Art
IR systems are known to include IR devices, which are in communication via IR communication paths. Each IR device includes an IR controller and an IR transceiver that includes a light generating diode and a light receiving diode. IR devices conduct point-to-point communication by sending and/or receiving infrared light pulses between IR transceivers.
The IR communication typically conforms to an IR standard protocol. Some IR standard protocols are provided by the Infrared Data Association (“IrDA”). IrDA defines standard protocols for IR physical layer communications in a specification titled “IrDA Physical Layer Specification v. 1.4,” published May 30, 2001. Other IrDA specifications are available at www.irda.org.
The IrDA physical layer specification is intended to facilitate the point-to-point communication between electronic devices (e.g., computers and peripherals) using directed half duplex serial infrared communications links through free space. IrDA defined four kinds of infrared links to support different data rates. Included in these links are Slow Infrared (SIR) supporting speeds up to 115.2 Kbps, Medium Infrared (MIR) supporting 0.576 Mbps and 1.152 Mbps data rates, Fast Infrared (FIR) supporting a 4.0 Mbps data rate, and Very Fast Infrared (VFIR) supporting 16.0 Mbps. Any utilization of the SIR, MIR, FIR or VFIR data transmission modes in this specification is referred to herein as “normal mode”.
The IrDA schemes in the normal mode utilize framing and the framing format varies from mode to mode. An IrDA frame typically includes a start of frame indication, an end of frame indication and data therebetween. For SIR mode, its frame format begins with one start bit (logic 0) followed by 8 data bits and optional parity bit(s), and ends with one or more stop bits. This format is an asynchronous format, because only one byte of data is transmitted/received in one frame. In contrast, the MIR, FIR, and VFIR format is a continuous format, in which there is no gap between frames. This provides for a continuous transmission, for which most IR transceivers are designed.
In at least some implementations of a standard SIR mode, a frame of data is received and then there is a gap of time before the next frame is received. This time gap is a problem for IR receivers that are designed for the continuous data flow of MIR, FIR, and/or VFIR, since they expect a continuous stream of data (i.e., one frame right after the other). To such IR receivers, the time gap of an SIR transmission is viewed as a transmission error.
Additionally, many IR devices are designed to comply with an industry standard mode of IR transmission. However, as with any standard, there are compromises to ensure general compatibility between devices. Such compromises include the overhead of framing and encoding in a normal mode. However, this framing overhead may slow data transmission from one device to another for certain applications and uses. In such applications and uses, a nonstandard, or “proprietary mode” may preferably be used between compatible devices.
Therefore, a need exists for a method and apparatus for a programmable infrared data processor without the above-referenced limitations.